chalda wrote:
Hello,
I have question about setting of compression of the ECW codec. I have
read the article on the page http://www.gdal.org/frmt_ecw.html and there
is said that option TARGET=percent sets size reduction as a percentage
of the original image.
I'm using the ECW codec through gdal_translate by this comma
gdal_translate -of JP2ECW -co "TARGET=10" input_image.tif out_image.jp2
But when I'm changing the number option of the TARGET then no change of
quality or the size of the image occurs. Or better the changes begins
around the number 50 but before all options 0-50 returs the same
"quality results".
By the mentioned page that shouldn't be correct. Could somebody explain
me please what how the quality option works here?
Ondrej,
The TARGET parameter sets a target reduction for the algorithm, but in
some cases low information images will be compressed more than requested.
If your image has a relatively low information density it may be that the
least compression the library is capable of providing is 50%.
The thing to keep in mind is that TARGET is a hint to the library - not
an exact definition of how much compression will be achieved.
Best regards,
--
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